Driveabbility - 15%, 17% or 19% reduction

[James@fomsport]

i have a GRS sat in the office at the moment and next to the GRS the finish on that looks awful

also bear in mind that is stock size so will not flow more air the GRS is much bigger than stock and achives a proper pressure drop (slows the air down in the i/c allowing it longer to cool)

[MAFFA]

I think i'll let that one go then on the basis of sound advice. Cheers fella

[DaFlake]

There is a bit more to an intercooler than just making it bigger. Beware of cheap knockoffs. I say pay up and go GRS....

[batou]

Quote: Originally Posted by MAFFA (original)

You know I think I can cope with a small reduction in fuel economy when i've come down from a BMW M5 where my combined MPG was around 17 .

I've been looking at alternative intercoolers in the states & came across the X02 intercooler which can be had for $300 delivered. Now things like this always seem to good to be true but i've been reading around on other forums (Impreza, Skyline etc...) & the feedback seems to be all positive.

What are your views? Any tried & tested? I'll do a search on here & see what I can find but for £150 delivered that's a hell of a saving over a £400 GRS intercooler

Cheers

MAFFA

+ VAT, Import duty etc?

My MPG has gone down massively on very short trips, if you nip around town or do anything under 10 miles I find it very poor. However, on A-B roads when doing around 100 ish miles I can get 27mpg driving spiritedly.

[Richard Crofts]

Or if your tracking and road use rather than rolling road or drag racing, consider a really big one like the GTT version. It suffers from heat soak compared to the GRS when in traffic or sitting waiting for the lights on the strip. But once the air flow is up the GTT works really well IMO.

[MINI-Morgan]

Quote: Originally Posted by batou (original)

+ VAT, Import duty etc?

My MPG has gone down massively on very short trips, if you nip around town or do anything under 10 miles I find it very poor. However, on A-B roads when doing around 100 ish miles I can get 27mpg driving spiritedly.

fuel dripping out the exhaust?

[cam213]

Why does everyone overlook the New Alta IC and the M7 IC? It looks to me like those would be top of the line as the flow is horizontal rather than vertical. I would not think the GRS would outperform them but I don't know. That's why I'm asking.

[James@fomsport]

as someone who sells both m7 and GRS, testing the in the states has shown the m7 and GRS to be evenly matched the GRS is also nearly £150 cheaper over here

[k-huevo]

Those style intercoolers require exit ducting, enhanced capture aperture, and thermal barriers, in order to perform any better than stock; also, their increased performance is limited to a narrow operating range which doesn’t include road racing.

The stock intercooler performs very well in a variety of environments. The GP IC performs better in conditions where there are adequate recovery times. That performance advantage comes from a well designed IC cover and under hood duct interface which does a very good job of cooling its additional rows.

Notice there are proponents of a particular aftermarket IC which have that product for sale. A clarification for one of those seller's statement about pressure drop; pressure drop is a bad thing unless it is offset by a much greater increase in density. Pressure drop is a bad thing when the cause is the result of being “slowed down” by obstructions. “Bigger” is not “better” if “smaller” has a greater efficiency percentage. That well spoken about aftermarket IC has repeatedly been shown to perform at least as well as OEM; if you have disposable income and a forgiving budget, get it for bling factor or perhaps the marginal cooling ability, but don’t expect miracles. Once again the money thing if that matters, for the cost involved stick with the OEM IC and direct funds towards changes that make a greater difference.

I’ve had the OEM pulley, 15% & 19% reduction pulleys, and currently have an 11.5%, plus more than a few different states of tune. I have a sophisticated diagnostic/logging program with which I’ve monitored those configurations, so there are data points to go along with my subjective observations. I’ve also logged other MINIs and can use that data for comparative evaluations. None of those size pulleys require a larger A/A intercooler (37C and higher ambient temps are common here); get an aftermarket TMIC for any other reason than “you have to”. Additional fueling is a good idea in the 6k rpm upwards region while using a 19%, so 380cc injectors with proper scaling could be, and was for me, beneficial. The 380s are a prudent addition when the OEM rev limiter is raised and/or improvements in volumetric efficiency are made, using any size pulley. I have seen other public data which would indicate larger than 380s are warranted when a 15% or smaller pulley is used on a highly VE improved motor with improved exhaust system in conjunction with a raised rev limiter. In my case 380s are and were OK & safe up to 7k rpm.

I know the questioning posters want simple sound byte answers, but the reality is more like “it depends” with many attached qualifiers. The term drivability is subjective, when I think of drivability throttle response comes to mind first, and a smaller pulley has a minor effect on that behavior compared to other potential modifications. Yes a 19% will provide noticeable, earlier improvements in real world torque, but so can a tune, and the torque effect can also be emulated by modifying targeted areas of the ECU’s program. Head work and exhaust improvements were major contributors to my power gains over stock baseline across the board; a much higher percentage than known increases attributable to a pulley reduction. For the perceived torque effect, the Sprint Booster device did more for low and midrange throttle response than any reduction in pulley size.

There is much myth surrounding the 19% and many willing to perpetuate those myths. The increased high rpm heat created by a 19% is less devastating than most advocate. Accommodations can be made to increase performance potential in deference to the higher heat generated by the 19% in the upper rpm range, however, in my opinion; the 19% is a performance option past its prime. It served me very well for a long time, with no evident damage, but there are other options currently available which can provide similar benefit. If you’ve already made the decision to go 19%, or already have it, enjoy.

[JerzyBondov]

So, k-huevo - you're saying that in your experience for someone like me (17% pulley, CAI, high temp plugs) the next most worthwhile upgrade would be a manifold, rather than an intercooler?

[k-huevo]

For anyone the most worthwhile upgrade is in driver education, most of us use only a fraction of the MINI’s potential.

Well executed head work is a great upgrade for beneath the bonnet. Gains can be realized at most rpm and load states, not just when the bypass valve closes. After that is when a header with larger flange ports and no pre-cat can work its best. Some improvement can be had since you’ve upped the boost but the cost/benefit ratio won’t be the same. If you decide to add a header, be sure to address the transition to the cat back so you don’t end up with a power robbing restriction. We’re getting off topic here (sorry MAFFA) but a less expensive alternative to an aftermarket header would be to remove the pre-cat on the OEM and if you get a ported head, the flange ports can be enlarged to match; that is unless the head’s exhaust ports are a mile wide.

[MAFFA]

k-huevo - Don't worry about going off topic as it's all good information to digest I'm loving getting back into the modifying again & a lot of the modifications are similar to the Impreza (if you ignore the SC/Turbo difference) as they are both forced induction.

Not sure i'll go full decat this time as I always hated getting the MOT done at my "friendly" garage about 50 miles away . Was a right pain. I'm thinking cat-back & then eventually sports cat just for the convenience.

Would a 15% reduction require the use of larger injectors then? Would a remap push them too far to keep up with the additional air. Would rather be safe than sorry & don't really want my injectors running at 95% when there is no need. Funnily enough i've a set of 380's in the shed but they're from my old Impreza so i'm sure they won't fit

MAFFA

[k-huevo]

You won’t know for sure if you need more fuel until AFR is recorded up to redline. If you decide to install 380s to ensure headroom, the ECU program should be modified accordingly.

[MINI-Morgan]

Yep the fuel maps need to matched to any injector size or the fuel pressure modified similarly.

[MAFFA]

Yeah I understand that. Still got a FPR & gauge lying around somewhere so could be the way forward. Might just go with 380's anyway to be safe.

I suppose the question then is whether I would need a custom "live" map or whether there are Bluefin maps etc... to take into account bigger injectors?

By the way guys thanks a lot for all this. Loving all the info.

MAFFA